WO 2011/039091 A1 describes in connection with a heart support system a pressure-measuring catheter which has a catheter hose and a pressure sensor for measuring the pressure distally of the catheter hose. Concretely, the pressure-measuring catheter has an optical pressure sensor and an elongate tube made of metal or a high-strength plastic, for example PEEK, through which a loosely laid optical fiber of the optical pressure sensor extends. At the anterior (distal) end of the pressure-measuring catheter there is located a sensor head which works on the Fabry-Perot principle. The sensor head possesses a cavity which is terminated by a thin, pressure-sensitive glass membrane, on the one hand, and into which the end of the optical fiber protrudes, on the other hand. The pressure-sensitive glass membrane is deformed in dependence on the size of the pressure acting on the sensor head. Through the reflection on the glass membrane, the light exiting from the optical fiber is modulatingly reflected and fed into the optical fiber again. At the proximal end of the optical fiber there is located an evaluation unit having an integrated CCD camera, which evaluates the obtained light in the form of an interference pattern. In dependence thereon, a pressure-dependent electrical signal is generated. Altogether this is thus an optoelectronic pressure sensor.
The pressure-measuring catheter is employed in connection with intravascular heart support systems, such as for example an intra-arterial balloon pump (IABP) or an intravascular rotary blood pump, by first advancing the relevant heart support system to the desired place in the patient's vascular system, i.e. for example into the aorta or into a heart chamber, by means of a catheter hose. The pressure-measuring catheter including the tube surrounding the optical fiber is displaceable relative to this catheter hose in its longitudinal direction and is subsequently introduced into the lumen of the catheter hose, advanced through the catheter hose and exits from its end. When the sensor head has reached the intended measurement location, the tube of the pressure-measuring catheter is withdrawn, but can also remain in situ as a permanent part of the pressure-measuring catheter. In connection with a rotary blood pump, it is proposed to push the pressure-measuring catheter far beyond the distal end of the catheter hose past the pump device of the rotary blood pump, so that it crosses the aortic valve and protrudes with its sensor head into the left ventricle to thereby measure the ventricular pressure.
A problem when navigating within the vascular system by means of catheters is curvatures, vessel branchings or obstacles to be crossed, such as for example cardiac valves. At such places the catheter can jam and bend back on itself due to its flexibility instead of pushing forward further. This is known as “kinking”. Such kinking is not always perceptible to the treating physician. Since the physiological pressure signals delivered by the pressure sensor are frequently ambiguous, it can hence happen that the physician fails to recognize the misplacement of the catheter, but mistakenly assumes that the catheter has reached the desired placement.
The object of the invention is hence to avoid mistakenly laying a catheter in a vessel of the patient, be it a blood vessel or another vessel, in the kinked state.
This object is achieved by the features of the independent claim. Claims dependent thereon state advantageous developments and embodiments of the invention.